Closed cell sponge weatherstrips have been the standard for years to seal vehicle closures against the passage of air and moisture. The weathership attaches to the vehicle body or closure around the opening (e.g. door or trunk opening). The weatherstrip preferably includes a tubular section that is designed to provide an interference sealing fit between the closure and body, and a mounting section to secure the weatherstrip in place. When the door or trunk lid is closed, the weatherstrip mechanically flexes according to the degree of interference. Generally, the greater the interference, the better the sealing function obtained.
Good sealing of closures is particularly desirable in vehicles such as automobiles, in order to isolate the passengers from inclement weather conditions; namely, precipitation as well as excessively hot or cold air. Additionally, it is also important to the comfort of the passengers in minimizing the annoying problem of wind noise in vehicles traveling at speed. It should be recognized, however, that the high degree of interference of the weatherstrip between the body and the closure required for good sealing disadvantageously results in increased closing effort.
Another consideration for vehicle weatherstrip design relates to an annoying problem known as "compression shock". With improved closure sealing, the rapid closing of a door or trunk lid in an otherwise closed vehicle often results in a momentary pressure surge or air compression in the passenger compartment. In essence, air is trapped inside the compartment and cannot escape past the tight weatherstrip seals around the various closures. This problem is particularly acute in designs where the closure moves substantially transverse to the body, such as in conventional swinging doors, trunk or hatchback lids. This compression shock not only further increases the closing effort required, but also results in an unpleasant feeling to the passengers.
Attempts to reduce door closing effort have in the past resulted in reduced sealing efficiency. Conversely, past attempts to emphasize improved sealing have resulted in a need for excessive closing effort. Neither of the above conditions is favored by consumers. Thus, automotive engineers have found it necessary to compromise these conflicting engineering requirements, with the best designs heretofore carefully balancing the relationship between sealing and closing effort.
Some efforts in the past have addressed these seemingly conflicting concerns and have provided some limited improvement. For example, spaced bleed apertures have been provided along the entire length of the weatherstrip allowing free communication between the atmosphere and the center of the weatherstrip. The bleed apertures are provided so that air is not entrapped within the weatherstrip and compressed when the closure is closed. More specifically, the apertures assure that the internal air pressure remains ambient at all times. Thus, mechanical flexing of the weatherstrip remains the principal medium for sealing with this improvement. Advantageously, by eliminating air entrapment in the weatherstrip, the closing effort for a rapidly closing door is reduced. Still, it should be recognized that this approach is not effective in improving the sealing efficiency since the interference fit is not appreciably increased.
Another idea that has gained some acceptance in the automotive industry is to apply at least two weatherstrips in juxtaposition to seal together when the door or lid is closed. The engaging parts of the weatherstrips are designed to form a labyrinth seal, and as a result, some improved sealing is obtained. Of course, with this arrangement, the degree of interference fit to allow easy closing is still sorely limited, and the cost of forming the seal and ultimately the cost to the consumer is substantially increased.
Another approach that has been used with success in the aircraft and aerospace industries is to make the weatherstrips inflatable. The basic idea is that when the door is closed, a positive pressure (greater than ambient pressure) is applied inside the closed tubular weatherstrip to provide expansion against the door and the door frame. The expanded weatherstrip provides increased interference, and therefore an improved seal. As will be recognized, this approach does reduce the door closing effort and compression shock to a degree because the non-inflated weatherstrip does not engage in an interference fit with the door and the door frame until the door is closed and the superatmospheric pressure is applied.
This concept, while useful in aircraft and aerospace vehicles, presents problems when attempts have been made to adapt it to general automotive use. First, in order to provide a closure sealing system using the superatmospheric pressure concept, a sophisticated air pressure supply system that is highly reliable must be provided. This is so since if air pressure is lost, a complete failure of the sealing function results and the interior is susceptible to damage from water leakage. Additionally, the passengers become exposed to the extremes of hot and cold atmospheric conditions and the annoyance of excessive wind noise. Furthermore, such a sophisticated air pressure system is relatively expensive, which is not conducive to the competitive pricing of a consumer product, such as an automobile.
Similarly, the superatmospheric inflated weatherstrip must not lose pressure over extended periods of time. To guard against this in an automotive system where small pinhole leaks are inevitable, especially after several years of use, supplemental means such as an electric pump would be required to periodically operate to maintain the optimum sealing pressure. Such a condition would inevitably lead to the need for an increased storage capacity of the electrical battery. Even with the increased battery size, under extended periods of inactivity of the automobile, the battery would discharge. Additionally, the superatmospheric pressure system must include relatively sophisticated regulators to compensate for variations in ambient pressure conditions, such as due to altitude and barometric pressure variations as well as temperature variations. Such additional cost adds to the prohibitiveness of using this type of system on a high volume consumer product, such as an automobile.
Another alternative is to provide a deflatable (rather than inflatable) weatherstrip, as disclosed in U.S. Pat. No. 2,908,948 to Jones. Jones teaches the use of an apparatus to deflate the weatherstrip upon opening of the closure. A piston working in a cylinder evacuates the weatherstrip. This apparatus has several drawbacks. For example, the problem of the inevitable wear and eventual leakage around the piston, especially after several years of service, is present. The piston working dry in the cylinder also provides undesirable high friction requiring a substantial force to operate. Furthermore, this increased force must be applied during opening movement according to the Jones patent, and is thus not readily adaptable to a small door, or to a trunk lid, where the opening force is applied by a counterbalancing spring. Finally, a relatively long and complicated linkage is required in the Jones system to provide the necessary stroke for providing the evacuating function.
The most effective approach to date for providing both improved sealing and easier closing of vehicular closures is set forth in U.S. Pat. No. 4,761,917 entitled "Deflatable Weatherstrips" of which I am a co-inventor. With this approach, a deflatable sealing member forms a weatherstrip to seal the opening in the vehicle body around the closure. The sealing member is connected to a vacuum source such as a bellows pump. The sealing member is deflated so as not to engage in an interference fit between the door and the closure. Unlike the Jones system, the deflation occurs during the closing movement when the manual force that can be applied is the greatest. In this manner, closing effort is reduced. Also, undesirable compression shock is eliminated. Following closing, the sealing member is vented to ambient pressure. This causes the sealing member to expand by inherent or built-in resilient memory to provide firm sealing engagement with increased resilient interference between the closure and the body.
While this approach is remarkably successful in reconciling the seemingly conflicting problems of excessive closing effort and tight sealing, the additional considerations of space limitations and design contraints led to the development of a bellows pump system which can be remotely mounted. This system is disclosed in my U.S. Pat. No. 4,805,347 entitled "Bellows System for Deflating Weatherstrips".
Here again, this approach has proven quite successful. However, in certain situations, the slightly increased opening force necessary to compress the bellows may not reflect the optimum design. In other words, a slight increase in closing force may, in certain situations, be more desirable than an increase in opening force. One example of this is with respect to trunk lids where it is more natural for the operator to apply a greater closing force. The present invention addresses this problem by providing a closure sealing system that is easier to actuate during closing movement.